Film processors, for example, those used to develop exposed X-ray films, conventionally process exposed photographic or X-ray film through at least two, and typically three, liquid chemical baths, and then through a dryer. The baths comprise at least a developer bath and a water wash bath, and if three baths are present, a fixer bath in between. The temperature of these baths is important and conventionally is controlled by heaters and heat exchangers.
More specifically, conventionally the temperature of the developer has been raised to its desired point, e.g., about 35.degree. C., by the use of a heater. However, the temperature of the developer frequently rises above this temperature. If left alone, the developer will heat up beyond its optimum temperature, and a heat exchanger is used to cool this hot developer liquid. Because the wash water of the last bath is optimally heated to at least about 4.degree. C., for optimum washing capability, it has been known to use the wash water as the heat sink in the heat exchanger.
Such wash water has been effective in driving the heat exchanger for the developer, but only when the source of the wash water, e.g., from the tap, is already at least 5.degree. C. less than the desired temperature of the developer leaving the heat exchanger. In some instances, for example, certain developing countries, such is not always the case. In such events, the water is unable to cool the developer sufficiently and the heat exchanger fails. The alternative of mounting a separate cooling unit on the source of wash water has been cumbersome and uneconomical.